How Much Rainwater is Too Much

[SwampeastMike]

Established 180-gallon planted tank will full animal load.

Tap water pretty nasty. It's "ph and softness adjusted" by the city and varies but typically ph 7.5-7.7 with kh 6 and gh 8. Have a water softener installed on the home system but always put it on bypass when using any tap water for replacement.

Now have a nice rainwater collection system and keep using more and more with water changes.

ph is around 6.8-7.0 with kh 3 and gh 5. All the residents are far happier with this ph than what comes from the tap. Ammonia and nitrites always 0.0 with nitrates in the 20-30 ppm range.

Am I correct that these are near ideal water conditions? Also correct that if I use more rainwater to get the ph down a bit more that kh in particularly will have to drop significantly thus allowing ammonia spikes?

Thanks for any advice.

 

[Caliban07]

Established 180-gallon planted tank will full animal load.



Tap water pretty nasty. It's "ph and softness adjusted" by the city and varies but typically ph 7.5-7.7 with kh 6 and gh 8. Have a water softener installed on the home system but always put it on bypass when using any tap water for replacement.



Now have a nice rainwater collection system and keep using more and more with water changes.



ph is around 6.8-7.0 with kh 3 and gh 5. All the residents are far happier with this ph than what comes from the tap. Ammonia and nitrites always 0.0 with nitrates in the 20-30 ppm range.



Am I correct that these are near ideal water conditions? Also correct that if I use more rainwater to get the ph down a bit more that kh in particularly will have to drop significantly thus allowing ammonia spikes?



Thanks for any advice.

You can add things to it to meet your requirements. Do you have a lot of farmland nearby? That’s a lot of nitrate in rain water. Plants will love that.

 

[SwampeastMike]

You can add things to it to meet your requirements. Do you have a lot of farmland nearby? That’s a lot of nitrate in rain water. Plants will love that.

Only thing I want to add is rainwater and tap water. Most tap water from the cold as the hot will always be softened on site. All of the tap water however is "softened and ph adjusted" in unspecified ways by the city. Such treatment also varies with the season with less in the dry summer months during peak demand.

I don't have any exact parameters to meet but do believe a naturally sustained ph of 6.8 at 77F temp provides abundant CO2 for a moderately planted, highly surface agitated tank. Is that correct?

LOTS of farmland but the rainwater is coming from my roof. Usually very pure but springtime pollen, flowers and other stuff from large trees in the area during a light rain. It provided some "black" water earlier that I used before rinsing out during a rainstorm, but most of that has been changed away by now. I use a large canister filter with plenty of media that bacteria love which the saltwater folk call "a nitrate factory." Also occasional dosing.

 

[Caliban07]

Only thing I want to add is rainwater and tap water. Most tap water from the cold as the hot will always be softened on site. All of the tap water however is "softened and ph adjusted" in unspecified ways by the city. Such treatment also varies with the season with less in the dry summer months during peak demand.



I don't have any exact parameters to meet but do believe a naturally sustained ph of 6.8 at 77F temp provides abundant CO2 for a moderately planted, highly surface agitated tank. Is that correct?



LOTS of farmland but the rainwater is coming from my roof. Usually very pure but springtime pollen, flowers and other stuff from large trees in the area during a light rain. It provided some "black" water earlier that I used before rinsing out during a rainstorm, but most of that has been changed away by now. I use a large canister filter with plenty of media that bacteria love which the saltwater folk call "a nitrate factory." Also occasional dosing.

Id always like some KH. Nitrification will always use some oxygen and alkalinity.

The nitrates probably come from intense muck spreading from poultry or pig farms.

You’re right not to use the softener. They replace calcium and magnesium ions with sodium and I think potassium.

 

[SwampeastMike]

Id always like some KH. Nitrification will always use some oxygen and alkalinity.

The nitrates probably come from intense muck spreading from poultry or pig farms.

You’re right not to use the softener. They replace calcium and magnesium ions with sodium and I think potassium.

Is the kh of 3 that I always measure adequate?

Just checked the water in the rain tank and it's 6.2 with all zeroes thereafter. That's the norm. The "black" water was from vegetable matter released by both conifers and deciduous trees.

 

[Caliban07]

Is the kh of 3 that I always measure adequate?



Just checked the water in the rain tank and it's 6.2 with all zeroes thereafter. That's the norm. The "black" water was from vegetable matter released by both conifers and deciduous trees.

Well there’s a few things to consider.

1) The test kit isn’t measuring KH it is measuring total alkalinity which is a bit misleading. There are a few things that can make up alkalinity which is what makes using the co2 chart inaccurate. As you know KH is only the carbonate hardness. Perhaps this is a bit lower than what your test kit is actually measuring.

2) Most of what we know about nitrification and biological filtration applies to wastewater treatment which uses very high ammonia loadings. Just like the microbes in your gut, the microbes in biological filtration will change based on a number of environmental factors and it has been shown that nitrification can still occur at lower pH levels so the importance of KH in aquarium settings needs to be taken with that in mind but I do think keeping some alkalinity is a logical option.

3) I like to keep some KH for my plants. They grow much better in low tech environments with some carbonates.

4) I like the black water for water changes. In general, If it has bugs in it it is safe for aquarium use and the pH isn’t an issue. You can add elements to it such as potassium bicarbonate or dolomite/aragonite to bring back some hardness.

Depends what fish you have and even then most will do well in many water conditions. Overall, if you can use rainwater I always would over any tap.

 

[SwampeastMike]

Carbonates in the local tap water https://dnr.mo.gov/ccr/MO4021532.pdf is around 250 ppm so I can't I easily use it to add the needed carbonates? I've normally been using about 1/3 tap water during water changes and the 3kh/5gh levels were consistent for months. Did two large changes with rainwater only recently and got the ph down to 6.8 from around 7.1

What kh using the API test do you suggest?

If true kh is usually somewhat lower than as tested by API then there should be good CO2 potential with it kept around 6.8ph at 75F, correct?

 

[Caliban07]

Carbonates in the local tap water https://dnr.mo.gov/ccr/MO4021532.pdf is around 250 ppm so I can't I easily use it to add the needed carbonates? I've normally been using about 1/3 tap water during water changes and the 3kh/5gh levels were consistent for months. Did two large changes with rainwater only recently and got the ph down to 6.8 from around 7.1



What kh using the API test do you suggest?



If true kh is usually somewhat lower than as tested by API then there should be good CO2 potential with it kept around 6.8ph at 75F, correct?

If you add a bit of tap you wont need to worry much about co2.

How are you calculating?

I don’t use test kits. I just use a conductivity meter and try to stay around the 300ppm range.

I reckon a KH of about 3 is a good target but there really is no perfect formula its all about trail and error. Doing what works for you. If you can match the parameters of a fishes natural body of water then great. If not just focus on keeping toxins down, oxygen high and feed good quality food including as much live as you can. I’m sure you already know most of that [emoji846]

 

[SwampeastMike]

How are you calculating? (CO2)

Just using the basic table showing ph, temp and theoretical co2 concentration. Nothing fancy at all. Know it's just an approximation even if I seem to have found a nice balance where all of the fish are very happy (ph 6.7 - 6.9) and the plants are OK.

Having never had water like this (slightly acid) I worry a bit about the ph "crashes" I read about when there is little buffering and a high bio load.

 

[Caliban07]

Just using the basic table showing ph, temp and theoretical co2 concentration. Nothing fancy at all. Know it's just an approximation even if I seem to have found a nice balance where all of the fish are very happy (ph 6.7 - 6.9) and the plants are OK.

Having never had water like this (slightly acid) I worry a bit about the ph "crashes" I read about when there is little buffering and a high bio load.

I ran my soft water tank tank with no water changes and rain water top ups for 12 months with no ill effects. Plants starved though. Except for the tiger lilly. That thing went insane on next to nothing. Probably using nutrients stored in the bulb.



You can use a floating plant to check for nutrient deficiencies. It has access to aerial co2 and is closest to the light so is likely to show deficiencies first theoretically.

Also plants love ammomia so I wouldn’t worry.